Numerous hydrocarbon reservoirs contain large volumes of gas associated with crude oil and hydrocarbon condensate. To produce a liquid hydrocarbon fraction for further processing, the associated gas is separated from the liquid hydrocarbons in a oil/gas production facility while the associated gas is often injected back to the hydrocarbon reservoir.
Where the oil/gas production facility is relatively close to a consumer, at least part of the associated gas may be further treated to the customer's specifications. On the other hand, where sale or other commercial use for the associated gas is not cost effective, the associated gas is frequently injected into a suitable formation to maintain a relatively steady rate of oil production. Alternatively, an oil/gas production facility may combine sale of one portion of associated gas with injection of another portion of the associated gas. However, as the gas injection pressure is typically at a much higher pressure than the sales gas pressure (e.g., 1500 psi to 3000 psi higher), separate injection gas compressors and sales gas compressors are normally required. Moreover, the rate of oil production depends to a significant degree on the sales gas demand. Consequently, when the sales gas demand declines, less associated gas is produced thereby reducing the oil production rate. To circumvent at least some of the problems associated with a reduced rate of sales gas, excess associated gas may be flared to maintain a relatively high production rate of liquid hydrocarbons. Flaring of associated gas, however, is environmentally problematic.
Among other obstacles, the relatively high cost of sales gas production from associated gas has a negative impact on commercial use of associated gas. For example, in most known methods of treating associated gas for sales gas production, the associated gas is first treated to remove acid gases, then dehydrated, and finally compressed to the sales gas pressure. Moreover, in cold climate environments, the sales gas must also be refrigerated to protect the permafrost. Such methods are relatively expensive, particularly when existing injection gas compression equipment is converted to sales gas compression (e.g., re-wheeling of injection gas compressors is often difficult and typically requires shutdown of at least part of the facility). The difficulties of such oil/gas facilities are often compounded by the use of an activated amine for acid gas removal. Activated amine solvents typically require extensive heating and cooling for absorption and regeneration, thereby adding significant cost and energy consumption. Moreover, activated amine solvents are often prone to freezing due to their high water content.
Therefore, although various configurations and methods for separation and processing of various hydrocarbon materials are known in the art, numerous problems still persist, especially where such configurations and methods are upgraded from associated gas injection mode to a combined mode where at least some of the associated gas is processed and sold to a consumer. Consequently, there is still a need for improved configurations and methods of gas processing.